Put the 6 cups of water into a soup pot and then place the leg quarter (with the skin on it) in it and then add the peeled onion, salt, and ground black pepper. Close the pot lid and bring the water to a boil and let them cook for about 45 minutes.
Remove the pot from the heat and set it aside. Take out the cooked chicken quarter from the pot and place it on a plate. Remove the skin and bones of the chicken and shred the chicken meat in a separate cup and set aside.
By using a strainer, filter the chicken broth in a separate bowl and set it aside.
Place the egg yolk and lemon juice in a cup and mix them well and set aside.
Put butter in the soup pot and melt it. And then add the filtered chicken broth back to the soup pot and bring the heat to medium level. Stir them for about 2 minutes to let the chicken broth and butter mix well.
Take two tablespoons of broth from the soup pot by using a ladle and add it to the egg yolk and lemon juice mix cup slowly. After you combine two tablespoons of broth with the egg yolk and lemon juice mix, add this mix back to the soup pot slowly. And then stir the broth well to let the all combine well.
Add the Orzo to the soup pot and close the lid and bring the broth to a boil and let them cook for about 10 more minutes.
And then add the shredded chicken meat into the soup pot and cook for about 5 minutes more.
Note: Garnish it with chopped parsley leaves and bread croutons.